From: Marc Zyngier <marc.zyngier@arm.com>
To: Mark Rutland <mark.rutland@arm.com>, Sinan Kaya <okaya@codeaurora.org>
Cc: dmaengine@vger.kernel.org, timur@codeaurora.org,
devicetree@vger.kernel.org, cov@codeaurora.org,
vinod.koul@intel.com, jcm@redhat.com, agross@codeaurora.org,
arnd@arndb.de, linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
christoffer.dall@linaro.org
Subject: Re: [PATCH V12 3/7] dma: add Qualcomm Technologies HIDMA management driver
Date: Fri, 15 Jan 2016 15:14:28 +0000 [thread overview]
Message-ID: <56990CD4.6020405@arm.com> (raw)
In-Reply-To: <20160115145629.GI3262@leverpostej>
On 15/01/16 14:56, Mark Rutland wrote:
> Hi,
>
> [adding KVM people, given this is meant for virtualization]
>
> On Mon, Jan 11, 2016 at 09:45:43AM -0500, Sinan Kaya wrote:
>> The Qualcomm Technologies HIDMA device has been designed to support
>> virtualization technology. The driver has been divided into two to follow
>> the hardware design.
>>
>> 1. HIDMA Management driver
>> 2. HIDMA Channel driver
>>
>> Each HIDMA HW consists of multiple channels. These channels share some set
>> of common parameters. These parameters are initialized by the management
>> driver during power up. Same management driver is used for monitoring the
>> execution of the channels. Management driver can change the performance
>> behavior dynamically such as bandwidth allocation and prioritization.
>>
>> The management driver is executed in hypervisor context and is the main
>> management entity for all channels provided by the device.
>
> You mention repeatedly that this is designed for virtualization, but
> looking at the series as it stands today I can't see how this operates
> from the host side.
Nor the guest's, TBH. How do host and guest communicate, what is the
infrastructure, how is it meant to be used? A lot of questions, and no
answer whatsoever in this series.
>
> This doesn't seem to tie into KVM or VFIO, and as far as I can tell
> there's no mechanism for associating channels with a particular virtual
> address space (i.e. no configuration of an external or internal IOMMU),
> nor pinning of guest pages to allow for DMA to occur safely.
>
> Given that, I'm at a loss as to how this would be used in a hypervisor
> context. What am I missing?
>
> Are there additional patches, or do you have some userspace that works
> with this in some limited configuration?
Well, this looks so far like a code dumping exercise. I'd very much
appreciate a HIDMA101 crash course:
- How do host and guest communicate?
- How is the integration performed in the hypervisor?
- Does the HYP side requires any context switch (and how is that done)?
- What makes it safe?
Without any of this information (and pointer to the code to back it up),
I'm very reluctant to take any of this.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2016-01-15 15:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-11 14:45 [PATCH v12 0/7] dma: add Qualcomm Technologies HIDMA driver Sinan Kaya
2016-01-11 14:45 ` [PATCH V12 1/7] dma: qcom_bam_dma: move to qcom directory Sinan Kaya
2016-01-11 14:45 ` [PATCH V12 2/7] dma: hidma: Add Device Tree support Sinan Kaya
2016-01-15 15:16 ` Mark Rutland
2016-01-15 15:30 ` Mark Rutland
2016-01-15 17:05 ` Sinan Kaya
2016-01-18 11:39 ` Mark Rutland
2016-01-15 16:49 ` Sinan Kaya
2016-01-18 11:49 ` Mark Rutland
2016-01-18 14:04 ` Sinan Kaya
2016-01-11 14:45 ` [PATCH V12 3/7] dma: add Qualcomm Technologies HIDMA management driver Sinan Kaya
2016-01-15 14:56 ` Mark Rutland
2016-01-15 15:12 ` Sinan Kaya
2016-01-15 15:22 ` Mark Rutland
2016-01-15 17:16 ` Sinan Kaya
2016-01-15 17:32 ` Marc Zyngier
2016-01-15 22:47 ` Sinan Kaya
2016-01-18 9:06 ` Marc Zyngier
2016-01-22 18:38 ` Sinan Kaya
2016-01-15 15:14 ` Marc Zyngier [this message]
2016-01-15 15:36 ` Mark Rutland
2016-01-15 16:01 ` Sinan Kaya
2016-01-20 22:18 ` Sinan Kaya
2016-01-15 15:40 ` Sinan Kaya
2016-01-15 17:28 ` Marc Zyngier
2016-01-15 17:44 ` Sinan Kaya
2016-01-15 18:08 ` Marc Zyngier
2016-01-11 14:45 ` [PATCH V12 4/7] dma: add Qualcomm Technologies HIDMA channel driver Sinan Kaya
2016-01-11 14:45 ` [PATCH V12 5/7] dma: qcom_hidma: implement lower level hardware interface Sinan Kaya
2016-01-11 14:45 ` [PATCH V12 6/7] dma: qcom_hidma: add debugfs hooks Sinan Kaya
2016-01-11 14:45 ` [PATCH V12 7/7] dma: qcom_hidma: add support for object hierarchy Sinan Kaya
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